Make the filling first. In a saucepan, combine the condensed milk, cream, shredded coconut, and butter; mix until combined.

Set the saucepan over low heat and cook gently, stirring constantly so nothing sticks. Once it starts to bubble, cook about 5 more minutes.

Off the heat, transfer the filling to a wide dish to cool faster — about 30-40 min, to room temperature.

While it cools, make the batter. Whisk 3 eggs (room-temperature is best) with the sugar until smooth and slightly lighter in color — no mixer needed.

Whisk in the oil, then the milk (also best not fridge-cold).

Sift the flour, cocoa, and baking powder together to break up lumps and spread the leavening evenly.

Whisk about half the dry mix into the wet until most of the flour disappears, then add the rest.

Line your pan (about 10x10 in / 25x25 cm) with parchment. Pour in half the batter and spread evenly into the corners, covering the bottom.

Spoon the room-temperature filling over the batter. Don't press or mix it in — keep it as a separate creamy layer in the center.

Pour the rest of the batter over the filling and gently spread to the corners without disturbing the coconut layer.

Bake on the middle rack at 350°F (180°C) for about 35-40 min. Let the cake cool completely to room temperature.

Meanwhile, make the ganache. Finely chop the chocolate into small, even pieces.

Heat the cream (ideally in a heavy-bottomed pan) over medium until you see steam and small bubbles at the edges. Pour it over the chocolate.

Stir gently until smooth and shiny — don't whip it, as bubbles dull the shine. Mix in the butter for extra shine and a softer set.

Let the ganache cool slightly. Leaving the cake in the pan, pour the warm ganache over the top and spread gently.

Slice with a sharp knife, pressing gently so you don't compress the cake or push out the filling; wipe the blade between cuts.

If you like, top with more shredded coconut and finely chopped chocolate.

Rest the cake at room temperature about 30 min so the ganache sets.